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Forschungszentrum Jülich

Impact of Dynamic Light on Photosynthesis

Application: Research & AgTech

Crop type: Arabidopsis

Dr. Shizue Matsubara at the Forschungszentrum Jülich in Germany is using programmable Helisospectra LEDs to study how dynamic changes in light intensity can affect the process of photosynthesis and plant performance.

Growers of both ornamental and edible crops know how important light is to the growth of their plants. Light, whether it’s natural or artificial, is an essential component of the photosynthetic process.

Dr. Shizue Matsubara, who is scientific associate at the Institute of Bio and Geosciences 2 (IBG-2) at the Forschungszentrum Jülich in Germany, is focusing her research on the dynamics of light.

“I am trying to understand how the process of photosynthesis in a plant adjusts its performance to changes in environments, especially light environments,” Matsubara said. “This is called light acclimation or photoacclimation. These changes or adjustments have been studied for many years, but mostly under constant light. Previous research has studied the response under constantly high or constantly low conditions.”

Matsubara said one of the reasons the research was limited was because of the type of lights that were available for research.
“There was no light source available to program rapid and dynamic changes (fluctuations) in the light intensity,” she said. “In other words, the light source with which the duration and intensity could be changed flexibly--both an increase and a decrease. With programmable Heliospectra L4A LEDs we can do that. We can program the lights so the light intensity can be changed very frequently in the course of a day or over several days or weeks. We can grow the plants under dynamic light conditions as found in natural environments and see how the photosynthetic apparatus develops and adjusts its properties.”

Matsubara is conducting her research in a controlled environment growth chamber. One of IBG-2’s growth chambers has been equipped with the Heliospectra LEDs.

There are seven different wavelengths in the Heliospectra LED lights that Matsubara is using.
“We are not looking at one wavelength,” she said. “There are many more wavelengths in natural light. The Helisospectra lights contain the wavelengths used by plants during photosynthesis.

“We have the capability of determining what the plant response would be under specific wavelengths. We could look at the effects of blue light or red light with the Heliospectra LEDs. The Heliospectra lights allow us to select only certain wavelengths and manipulate the intensity of only those wavelengths. Interaction between light fluctuation and wavelength composition is a question for future studies.”

STUDYING THE “MODEL” PLANT

Matsubara is doing her research with the plant Arabidopsis thaliana.

“It is the model plant for plant biology,” she said. “This is the first plant that the genome information was made available. Most basic research in the plant sciences uses Arabidopsis.

“I am working with different ecotypes collected from different parts of the world. I am also working with transgenic mutants. This is why I am using a model plant because there are so many different mutants and transgenic plants available to identify underlying mechanisms and genes that play a central role.”

PROGRAMMABLE, ENERGY-EFFICIENT LED LIGHTS

Matsubara is studying the light conditions that plants commonly grow under for low and high light.

“We are looking at the light conditions that plants commonly grow under for low and high light,” she said. “The lowest intensity that we are using with the Heliospectra LEDs is 50 micromoles. We could go lower. Growing plants at around 100 micromoles is a typical light condition in growth chambers. The highest light intensity that can be achieved with the Heliospectra LEDs is above 1,000 micromoles. We are changing the light intensity within this range. With the Heliospectra LEDs we can program dynamic changes in the light intensity, which is not possible with other conventional light fixtures.”

Another advantage to using the Heliospectra LEDs in the growth chamber is the amount of energy that is used.
“The Heliospectra LEDs do not generate much heat compared with conventional strong light sources,” Matsubara said. “This allows us to study the effect of light intensity on plants separate from the effects of heat.
“The more heat is given off by the light, the more the air has to be cooled inside the growth chamber. We would need more energy to control the conditions if substantial heat is being generated by the lights.

“Also, if heat is generated by the lights we cannot control the temperature if the leaves heat up. We cannot control the leaf temperature. Even under the LED lights the temperature of the leaves increases a little bit, maybe 1ºC, under the fluctuating light conditions we use, but it is a minimal amount. With the Heliospectra LEDs we don’t have to be concerned with raising the temperature of the plants. Halogen lamps, for example, emit far more heat than photosynthetically active light.”

DOING BASIC RESEARCH

The studies Matsubara is conducting are focused on basic research.
“We want to know how plants respond to dynamic light environments for long term periods,” she said. “Not just for a few minutes or a few hours, but for many days. We therefore grow the plants under these dynamic conditions. We found a way to apply light fluctuations in the growth chamber to selectively enhance a defense response in plants. Now we also want to find out whether such effects of dynamic light help plants to better cope with other abiotic and biotic stress conditions in natural environments.

Matsubara said the earliest that the plants are placed into the growth chamber is when they have their first true leaves. The plants are sometimes kept under the LED lights until they flower.

“How do the plants respond to the light environment during different stages of their life cycle? To understand that is one of the goals of my research,” Matsubara said.